International application PCT/AU92/00645 entitled "Reactor" lodged on Dec. 2, 1992 in the name of the applicant discloses a reactor for aerating a fluid with a gas.
The reactor comprises a mixing tank for the fluid, a centrally located draft tube that partitions the mixing tank into a central chamber and an annular chamber which are in fluid communication at upper and lower regions of the mixing tank, and an axial flow pump located in the draft tube for circulating the fluid downwards in the draft tube and upwards in the annular chamber. The reactor also comprises an external circuit that removes a sidestream of the fluid from the mixing tank, aerates the fluid, and returns the aerated fluid to the mixing tank. The external circuit comprises an aerator in the form of a venturi of frusto-conical design having holes or a porous membrane in the region of the throat of the venturi for introducing the gas into the fluid. The aerator takes advantage of the fact that the fluid pressure in the throat region of the venturi is less than that upstream and downstream of the throat region and enables the air to be introduced into the liquor by natural aspiration or at low pressure. The external circuit further comprises a centrifugal pump for pumping the fluid around the external circuit.
The reactor disclosed in the International application is an effective means of aerating a fluid. This is reflected in the experimental results in the International application which show a decrease in power requirements with the reactor when compared with a conventional air agitated reactor.
An object of the present invention is to provide a reactor for introducing a gas into a fluid which is capable of achieving a further significant decrease in power requirements when compared with the reactor disclosed in International application PCT/AU92/00645.